The present invention generally relates to non-reciprocal circuit elements and a method of manufacturing them, and more particularly, the improved construction of non-reciprocal circuit elements to be adopted as high-frequency parts for use in a microwave band such as isolators, circulators, and a method of manufacturing them.
Generally, non-reciprocal circuit elements such as isolators, circulators or the like have such a function that the attenuation is hardly effected in the transmission direction of signals, and the attenuation becomes larger in an opposite direction to the transmission direction. The non-reciprocal circuit elements are adopted in a transmission circuit portion of a mobile transmission appliance such as a portable telephone, automobile telephone or the like to be used in, for example, a UHF band. Non-reciprocal circuit elements to be adopted in the mobile communication appliance are demanded to be smaller in size and lighter in weight, considering the uses thereof. Conventionally, methods of intensively disposing central electrodes and matching circuits on one basic plate are variably proposed. The construction of such a non-reciprocal circuit element will be described hereinafter.
(1) First Prior Art
FIG. 56 and FIG. 57 are views showing the construction in a first example (hereinafter referred to as a first prior art) of the conventional circulator. Especially, FIG. 56 is a perspective view of the essential portions thereof, and FIG. 57 is a sectional view thereof. Three sets of central electrodes 2a, 2b are disposed at given angle intervals so that they may not come into contact against one another, and may not cross with respect to one another, as shown in FIG. 56, on the surface of the dielectric basic plate 1 of ceramic or the like. Three sets of central electrodes 2c, 2d are disposed at given angle intervals, so that they may not come into contact against one another, and may not cross with respect to one another similarly, on the reverse face of the dielectric basic plate 1 of ceramic. The respective central electrodes 2a, 2b are respectively connected with the respective central electrodes 2c, 2d of the reverse face through a plurality of through holes 5. Three capacity electrodes 3 are formed integrally with the central electrodes 2a, 2b around the respective central electrodes 2a, 2b on the surface of the dielectric basic plate 1. An earthing electrode 4 is formed integrally with the central electrodes 2c, 2d around the respective central electrodes 2c, 2d on the reverse face of the dielectric basic plate 1. The respective capacity electrodes 3 are opposed to the earthing electrode 4 with the dielectric basic plate 1 between them so as to constitute a capacitor for matching circuit use.
As shown in FIG. 57, the dielectric basic plate 1 is accommodated into the interior of a metallic yoke 7. An earth plate 8 is disposed below the dielectric basic plate 1 in contact with the earth electrode 4 on the reverse face of the dielectric basic plate 1. A concave portion is provided in the central portion of the earth plate 8 with a ferrite plate 6 being engaged into the concave portion. The ferrite plate 6 is positioned below the respective central electrodes so as to help the inductive coupling of the respective central electrodes. A magnet 9 is fixed onto the inner ceiling face of the yoke 7. The magnet 9 applies a direct current magnetic field with respect to each of the central electrodes.
(2) Second Prior Art
FIG. 58 and FIG. 59 show the construction of a second example (hereinafter referred to as a second prior art) of the conventional circulator. Especially, FIG. 58 is a perspective view of the essential portions thereof, and FIG. 59 is a sectional view thereof. An earth electrode 4 is formed as shown in FIG. 58 on the reverse face of a dielectric basic plate 1 such as ceramic or the like. Three electrode films having predetermined shapes, referred to herein as "pattern shapes 10" and two insulating sheets 11 are alternately formed by the repetition of printing and co-firing operations and are thereby sintered on the surface of the dielectric basic plate 1. Each of the electrode films of pattern shapes 10 has a central electrode portion 20 and a capacity electrode portion 30. One end of each of the central central electrodes 20 is connected with the earth electrode 4 on the reverse face respectively through a through hole 5. Each of the capacity electrode potions 30 is opposite to the earth electrode 4 with the dielectric basic plate 1 being therebetween so as to constitute a capacitor for matching circuit use.
The sectional construction of the second prior art is similar to the sectional construction of the above described first prior art as shown in FIG. 59.
(3) Third Prior Art
FIG. 60 and FIG. 61 are views showing the construction of a third example (hereinafter referred to as a third prior art) of the conventional circulator. Especially, FIG. 60 is a perspective view of the essential portions thereof, and FIG. 61 is a sectional view thereof. Electrode films of pattern shapes 10a, 10b and 10c are respectively formed by the printing operation on the surfaces of the dielectric basic plates 1a, 1b and 1c of a ceramic or the like. The earth electrodes 4a, 4b and 4c are respectively formed by the printing operation on the reverse face of the dielectric basic plates 1a, 1b and 1c. The electrode films of pattern shapes 10a, 10b and 10c respectively include central electrode portions 20a, 20b and 20c, capacity electrode portions 30a, 30b and 30c, and earth electrode portions 40a, 40b and 40c. The dielectric electrode basic plates 1a, 1b and 1c are individually fired, and thereafter are adhered under pressure to form a multi-layer basic plate. The earth electrode portions 40a, 40b, 40c, and earth electrodes 4a, 4b, 4c are connected with respect to one another through through holes 5. Each of the capacity electrode portions 30a, 30b and 30c are respectively opposite to the earth electrodes 4a, 4b and 4c with the dielectric basic plates 1a, 1b and 1c being therebetween so as to constitute a capacitor for matching circuit use.
The sectional construction of the third prior art is somewhat similar to the sectional construction of the above described first prior art as shown in FIG. 61.
The first through third prior arts described hereinabove have various problems as described hereinafter.
(1) First Prior Art Problem
a. Through holes are required without fail to permit crossing of the central electrodes without the respective central electrodes being short-circuited with respect to one another, thus resulting in complicated construction and higher cost.
b. Width of the central electrode has to be made narrower in order to prevent short-circuiting among the central electrodes. Therefore, the loss at the central electrode increases, thus resulting in deteriorated electric characteristics.
c. The capacity electrodes 3 are disposed around the respective central electrodes 2a, 2b. Area of the capacity electrodes 3 has to be made larger in order to obtain necessary capacity values so that the construction of the whole element is made larger in size.
d. Two co-firing steps are required, namely, a co-firing step to sinter a dielectric basic plate 1, and a co-firing step to sinter an electrode printed on the dielectric basic plate 1, thus resulting in complicated manufacturing and longer manufacturing time.
e. A wiring operation is required between the dielectric basic plate and the circuit basic plate in the mounting operation on the external circuit basic plate, thus resulting in complicated and troublesome mounting operation.
(2) Second Prior Art Problem
a. Capacity electrode portions 30 are disposed around the respective central electrode portions 20. Area of the capacity electrode portions 30 has to be made larger so as to obtain the necessary capacity value, thus resulting in larger size of the whole element.
b. The co-firing steps to sinter the respective electrode films of pattern shapes 10 and the respective insulating sheets 11 are repetitively required, thus resulting in complicated manufacturing and longer manufacturing time.
c. A wiring operation is required between the dielectric basic plate and the circuit basic plate in the mounting operation on the external circuit basic plate, thus resulting in complicated and troublesome mounting operation.
(3) Third Prior Art Problem
a. The capacity electrodes 30a through 30c are disposed around the respective central electrodes 20a through 20c. Area of the capacity electrodes 30a through 30c has to be made larger in order to obtain the necessary capacity value so that the construction of the whole element is made larger in size.
b. The co-firing steps to sinter each of the respective dielectric basic plates 1a though 1c are repetitively required, thus resulting in complicated manufacturing and longer manufacturing time.
c. Connecting locations are increased in number so that reliability is inferior.
d. It is difficult to make thinner each of the dielectric basic plates 1a through 1c. Therefore, the thickness of the whole element becomes larger and the intervals between the central electrodes located on the lower layer and the upper layer become too far, which unbalances the mutual couplings because the equivalent circuit constants of the central electrodes are unequal.
e. A wiring operation is required between the dielectric basic plate and the circuit basic plate in the mounting operation of the non-reciprocal circuit element on the external circuit basic plate, thus resulting in a complicated and troublesome mounting operation.